1. Field of the Invention
The present invention relates to a screen which displays an image by projection light, and more particularly to a reflective screen and a method for manufacturing the same.
2. Description of Related Art
In recent years, as means of presenting materials in a conference and the like, data projectors are widely used, and video projectors and moving picture film projectors for home use are being spread. In these projectors, light emitted from a light source is spatially modulated by a light valve to form light image, and the light image is projected on a screen for projection through a lighting optic, such as a lens.
The projectors of this type include one which allows color images to appear using, as a light source, a lamp emitting white light including light of three primary colors, i.e., red (R), green (G), and blue (B) light, and using a transmissive liquid-crystal panel as a light valve. In this projector, white light emitted from the light source is split by a lighting optic into light rays of red, green, and blue, and the individual light rays are converged to predetermined optical paths. These light fluxes are spatially modulated by the liquid-crystal panel according to the image signals, and the modulated light fluxes are combined by a light combining unit to form color light image, and the color light image combined is magnified by means of a projection lens and projected on a screen.
Further, recently, as a projector which allows color images to appear, an apparatus using a narrow-band three primary-color light source as a light source, for example, a laser generator emitting narrow-band light of the three primary colors, and using a grating light valve (GLV) as a light valve has been developed. In this projector, light fluxes of the individual colors emitted from the laser generator are spatially modulated by the GLV according to the image signals. The modulated light fluxes are combined by a light combining unit like in the above-mentioned projectors to form color light image, and the color light image combined is magnified by means of a projection lens and projected on a screen.
In the above projectors, the screen which displays a projection image is roughly classified into a transmissive screen and a reflective screen. The transmissive screen is a screen which transmits light image emitted from a projector in the rear of the screen so that a projection image can be seen as the transmitted light, and the reflective screen is a screen which reflects light image emitted from a projector in front of the screen so that a projection image can be seen as the reflected light.
As the reflective screen, a beads screen or white screen which reflects and scatters projection light from a projector is used, and this screen also reflects light other than the projection light, i.e., ambient light, and hence not only the ambient light level but also the black level (black image luminance) are increased, and therefore the screen can display only an image having a low contrast (=white level/black level) in the bright light at a high ambient light level, and thus the room must be dim for lowering the ambient light level.
For solving the problem, there has been proposed a screen in which a light absorbing layer is formed in front of a reflective layer to lower the black level, improving the contrast in the ambient light (see, for example, patent document 1 below). However, in this case, the light absorbing layer absorbs not only the ambient light but also the projection light, and therefore the white level is lowered to reduce the screen gain (luminance), and further the improvement of the contrast in the bright light is not satisfactory.
In addition, there has been proposed a screen shown in FIG. 25, in which a transparent layer 103 having a plurality of protrusions 102 is formed on a diffuser panel 101 on the surface of the screen and an opaque layer 104 including a black coating composition is formed on the sidewall of each protrusion to absorb ambient light, improving the contrast in the ambient light without lowering the white level (see, for example, patent document 2 below). However, in this case, the ambient light from the front of the screen is not absorbed and the improvement of the contrast in the bright light is not satisfactory, and further there is a problem in that a prolonged time and a cumbersome process are required in forming the protrusions and the opaque layer on the sidewall of each protrusion.    [Patent document 1] Japanese Patent No. 3103802    [Patent document 2] Japanese Patent No. 2889153